The research activity of the Theory Group at LNS belongs to the vast field of Nuclear Physics aiming at the understanding of nuclei and nuclear matter, from its normal conditions to the extreme situations of density and temperature that are reached in supernovae explosions, compact stellar objects, Early Universe evolution and in heavy-ion collisions at ions accelerators and colliders.
Nuclei are a very complex many-body system with three of the four fundamental interactions at work (strong, weak and electromagnetic), challenging experimentalists and theorists for many decades. Hence a sensible theory should be able to describe the nuclear spectra, as well as the electromagnetic, weak, and strong transitions that lead to the excitations of those states in nuclear reactions, or characterize their decay properties. Moreover, the behavior of nuclear matter in various conditions of density, temperature and asymmetry in the neutron-proton content, as they can be encountered in compact stellar objects, is extremely fascinating to understand. The exploration of the full nuclear matter phase diagram, and the characterization of the nuclear Equation of State (EoS) are among the mail goals of nuclear reaction studies, involving in particular heavy ion experiments.u
The theoretical activity at LNS develops within two national projects of INFN (see description below): MONSTRE (MOdeling Nuclear STructure and REactions), SIM (Strongly Interacting Matter: matter under extreme conditions).
The main scope of the MONSTRE project is to build a unified framework for the study of atomic nuclei, nuclear reactions, and strongly interacting matter. In particular, the project aims at merging the most recent developments of nuclear structure and reaction theory, in order to provide support to the most challenging experimental projects related to the investigation of rare isotopes, dark-matter detection, and electroweak physics, including neutrino-oscillation and double-beta decay. The project is composed by three main lines of research: i) modern nuclear interactions and ab-initio techniques; ii) many-body methods and iii) merging of structure and reaction theories. The LNS unit is actively involved, also through many international collaborations, in all these studies. Particular attention is devoted to the study of heavy ion double charge exchange reactions related to the NUMEN project, by coupling advanced nuclear structure models (based on the EDF theory) and quantum scattering techniques. Reactions of current experimental interest, also for neutrino-less double beta decay studies, will be investigated, with possible high-impact implications in particle physics, neutrino physics and nuclear physics. Nuclear medicine applications are also studied. Upgraded semi-classical transport theories will be applied to fragmentation reactions of interest for medical applications, involving light ions at intermediate beam energies.
In particle accelerators it is possible to collide heavy-ions at such energies that a new state of matter is generated: the Quark-Gluon Plasma. The aim is to study the properties of such matter that has permeated the first microseconds after the Big-Bang and to understand how it undergoes a phase transition becoming the ordinary matter made by the protons and neutrons constituting the nucleus of atoms. In such collisions one creates a matter at trillions of degrees (1012 K) for a time of the order of hundreths of zeptoseconds (10-23 seconds). The Theory group at LNS has extended the theoretical techniques of nuclear physics to describe the evolution of the matter created in the experiments at LHC-CERN in Geneva and at the RHIC-BNL in Long-Island, interpreting the results and suggesting new measurements . The group participates to the national project SIM devoted to such studies in collaboration with Catania, Florence and Turin, and with several international Institutes.